Calculator Objective-C

//
//  main.m
//  Started
//
//  Created by Bruno Monteiro on 10/06/13. (Aka Brinuz)
//

#import <Cocoa/Cocoa.h>

@interface Calculator : NSObject
{
	int num1;
	int num2;
}

-(void) askNums;
-(void) doAddition;
-(void) doSubtraction;
-(void) doMultiplication;
-(void) doDivision;

@end

@implementation Calculator

-(void) askNums {
	NSLog(@"First Number:");
	do {
		scanf("%d",&num1);
	} while (num1 == 0); //Don't want it to be 0
	
	NSLog(@"Last Number:");
	do {
		scanf("%d",&num2);
	} while (num2 == 0); //Don't want it to be 0
}

-(void) doAddition {
	NSLog(@"Result: %d", num1 + num2);
	NSLog(@"\n\n");
}

-(void) doSubtraction {
	NSLog(@"Result: %d", num1 - num2);
	NSLog(@"\n\n");
}

-(void) doMultiplication {
	NSLog(@"Result: %d", num1 * num2);
	NSLog(@"\n\n");
}

-(void) doDivision {
	NSLog(@"Result: %d", num1 / num2);
	NSLog(@"\n\n");
}

@end

int menu();

int main(int argc, char *argv[])
{	
	Calculator *calc = [[Calculator alloc] init];
	int option;
	
	do
	{
		option = menu();
		if(option == 0)
		{
			NSLog(@"Will Exit...");
			return 0;
		}
		
		[calc askNums];
		
		switch (option) {
			case 1:
				[calc doAddition];
				break;
			case 2:
				[calc doSubtraction];
				break;
			case 3:
				[calc doMultiplication];
				break;
			case 4:
				[calc doDivision];
				break;
		}
	}
	while (option != 0);
	
	return 0;
}

int menu()
{
	NSLog(@"Option:");
	NSLog(@"1- Add. \n");
	NSLog(@"2- Sub. \n");
	NSLog(@"3- Multi. \n");
	NSLog(@"4- Div. \n");
	NSLog(@"0- Exit");
	
	int option = 0;
	
	do {
		NSLog(@"Choose Option:");
		scanf("%d",&option);
	} while(option < 0 || option > 4);
		
	return option;
}